Surgical robot system and external force measuring method thereof

PURPOSE: A surgical robot system and an external force measuring method thereof are provided to implement a solid sense device by indirectly obtaining information about an operational force of an instrument. CONSTITUTION: A surgical robot system includes a driving motor(120) and a controller(110). The driving motor outputs an encoder signal corresponding to state information of the system. A controller calculates an external force applied to an instrument(130) using an SMCSPO(Sliding Mode Control with Sliding Perturbation Observer) algorithm. A controller includes a perturbation observer and a sliding state observer. The state observer estimates a state variable for calculating a perturbation value using the state information of the system. The perturbation observer calculates the perturbation value using the estimated state variable.